Astm b 537 70 (2013)

Designation B537 − 70 (Reapproved 2013) Standard Practice for Rating of Electroplated Panels Subjected to Atmospheric Exposure1 This standard is issued under the fixed designation B537; the number imm[.]

Designation: B537−70 (Reapproved 2013)

Standard Practice for

Rating of Electroplated Panels Subjected to

This standard is issued under the fixed designation B537; the number immediately following the designation indicates the year of

original adoption or, in the case of revision, the year of last revision A number in parentheses indicates the year of last reapproval A

superscript epsilon (´) indicates an editorial change since the last revision or reapproval.

1 Scope

1.1 This practice covers a preferred method for evaluating

the condition of electroplated test panels that have been

exposed to corrosive environments for test purposes It is based

on experience in use of the method with standard 10- by 15-cm

(4- by 6-in.) panels exposed on standard ASTM racks at

outdoor test sites in natural atmospheres It has been used also

for rating similar panels that have been subjected to accelerated

tests such as those covered by Practice B117, MethodB287,

Test MethodB368, and Test MethodB380 Any modifications

needed to adapt the method to rating actual production parts are

not considered in this practice

1.2 This practice refers only to decorative-protective

coat-ings that are cathodic to the substrate, typified by nickel/

chromium or copper/nickel/chromium on steel or zinc die

castings It is not intended for use with anodic sacrificial

coatings such as zinc and cadmium on steel

2 Referenced Documents

2.1 ASTM Standards:2

B117Practice for Operating Salt Spray (Fog) Apparatus

(Withdrawn 1987)3

B368Test Method for Copper-Accelerated Acetic Acid-Salt

Spray (Fog) Testing (CASS Test)

B380Test Method for Corrosion Testing of Decorative

Electrodeposited Coatings by the Corrodkote Procedure

2.2 ASTM Adjunct:4

Dot charts (9 charts, 81⁄2by 11 in.) (9 color photos, 3 by 5 in.)

3 Basis of Procedure

3.1 The rating method described in this recommended practice is based on the recognition that typical decorative-protective deposits such as nickel/chromium, with or without a

copper undercoat, have two functions: ( 1) to protect the

substrate from corrosion and thus prevent degradation of appearance caused by basis metal corrosion products (for

example, rust and rust stain); and (2) to itself maintain a

satisfactory appearance Although these functions overlap, they can be evaluated separately and it is frequently desirable to do

so Accordingly, this practice assigns separate ratings to (1) appearance as affected by corrosion of the substrate and (2)

appearance as affected by deterioration of the coating itself 3.2 The rating number assigned to the ability of the coating

to protect the substrate from corrosion is called the “protec-tion” number or rating

3.3 The rating number assigned to the inspector’s judgment

of the overall appearance of the panel, including all defects caused by the exposure (Note 1), is called the “appearance” number or rating

N OTE 1—Panels that are not “perfect” even before being exposed should normally be rejected (see Note 4 ).

3.4 The result of inspecting a panel is recorded as two numbers separated by a slash (/), the protection number being given first

3.5 In addition to recording the numerical rating of a panel, the inspector should note the type(s) and severity of defect(s) contributing to the rating This may be done by the use of agreed symbols for the most common defects (Appendix X1) and abbreviations for degree or severity of these defects

1 This practice is under the jurisdiction of ASTM Committee B08 on Metallic

and Inorganic Coatingsand is the direct responsibility of Subcommittee B08.05 on

Decorative Coatings.

Current edition approved Dec 1, 2013 Published December 2013 Originally

approved in 1970 Last previous edition approved in 2007 as B537 – 70 (2007).

DOI: 10.1520/B0537-70R13.

2 For referenced ASTM standards, visit the ASTM website, www.astm.org, or

contact ASTM Customer Service at service@astm.org For Annual Book of ASTM

Standards volume information, refer to the standard’s Document Summary page on

the ASTM website.

3 The last approved version of this historical standard is referenced on

www.astm.org.

4 Color reproductions of these photographs are available from ASTM Interna-tional Headquarters Order Adjunct No ADJB0537 Original adjunct produced in 1987.

4 Types of Defects

4.1 “Protection” defects include crater rusting (Note 2),

pinhole rusting, rust stain, blisters (Note 3), and any other

defects that involve basis metal corrosion

N OTE 2—“Rusting” or “rust” as used in this document includes

corrosion products of the substrate and is not confined to iron or steel: the

white corrosion products of zinc die castings and aluminum, for example,

are included in this term.

N OTE 3—Blisters on plated zinc die casting usually connote basis metal

corrosion; but the inspector’s judgment may be required to decide whether

a blister does or does not arise at the substrate-coating interface.

4.2 “Appearance” defects include, the addition to those

caused by basis metal corrosion, all defects that detract from

the appearance (that is, the commercial acceptability) of the

panel Typical are: surface pits, “crow’s feet,” crack patterns,

surface stain, and tarnish

4.3 Defects developing on exposure that reflect improper

preparation or plating should be noted but no attempt should be

made to rate panels showing major amounts of such defects

Peeling of the coating from the substrate, or of one coat from

another, is the principal such defect

5 Preparation for and Manner of Inspection

N OTE 4—It may be desirable to expose panels for test even though they

are defective in certain respects before exposure In that case, an

inspection should be made and recorded before the panels are exposed.

5.1 Panels may be inspected on the exposure racks or may

be removed to a more suitable location if necessary Lighting

during inspection should be as nearly uniform as possible;

direct reflection from sun or clouds should be avoided, and

various angles of inspection should be tried to ensure that

defects show up

5.2 If the condition of the panels allows, inspection should

be made in the “as-is” condition If dirt, salt deposits, and so

forth, make it impractical to inspect them, panels may be

sponged with a mild soap solution followed by water rinse; but

no pressure should be exerted in this procedure such as would

tend to upgrade the rating by, for example, cleaning off rust or

rust stain Panels should be allowed to dry before inspecting

them

5.3 Defects to be noted and taken into account in rating

panels include only those that can be seen with the unaided eye

(Note 5) at normal reading distance

N OTE 5—“Unaided eye” includes wearing of correctional glasses if the

inspector normally wears them.

5.3.1 Optical aids may be used to identify or study defects

once they are found by unaided eye inspection

5.4 Edge defects, occurring within 6.5 mm (1⁄4 in.) of the

edges of a panel, may be noted in the description but are not

counted in arriving at the numerical rating Similarly contact

and rack marks, mounting holes, and so forth, should be

disregarded

6 Assignment of Protection Rating

6.1 The numerical rating system is based on the area covered by protection defects, by the following equation:

where R = rating and A = percentage of the total area cov-ered by defects R is rounded off to the nearest whole number,

leading to the tabulation given inTable 1 6.1.1 Strict application of the equation given in6.1would lead to ratings greater than 10 for panels with extremely small defective areas Rating 10, accordingly, is arbitrarily assigned

to a panel with no defects, and the equation operates at ratings

9 and below

6.1.2 If desired, fractional ratings between 9 and 10 may be assigned to panels judged better than 9 but not perfect Fractional ratings below 9, although normally not especially useful, may be assigned if desired

6.2 As an aid in judging the defective area, standards of comparison, consisting of photographs of panels or of dot charts are made part of this practice SeeAppendix X2 These photographs and charts4 are 10 by 15 cm (4 by 6 in.) to facilitate comparison with the panel being inspected The standards represent as nearly as possible the maximum amount

of corrosion permissible for a given rating; there is a standard for each rating 1 through 9 A panel worse than the standard for rating 1 would rate 0

6.2.1 The types of corrosion defects normally encountered differ according to the type of atmospheric exposure Typical decorative deposits exposed to marine atmospheres often tend

to fail by crater rusting, whereas in industrial atmospheres, they are more likely to exhibit pinpoint rusting; and the latter atmosphere also tends to be more severe with regard to degradation of the coating system but somewhat less severe with regard to basis metal corrosion For this reason, the same standard comparison photographs or charts are not suitable for use at both types of locations; photographs are more helpful in assessing panels exposed to marine atmospheres, whereas dot charts can be used for industrial locations (Appendix X2) 6.3 In rating any given panel, it is recommended that the appropriate series of standards be placed beside it and the basis metal corrosion defects in the panel be matched as nearly as possible with one of the standards If the panel is somewhat

better than standard (X) but not as good as standard (X + 1) it

is rated (X); if somewhat worse than standard (X) but not as bad

TABLE 1 Protection Rating Versus Area of Defect

as standard (X − 1) it is rated (X − 1) At the inspector’s option,

decimal fractional ratings may be assigned

6.3.1 If a large group of panels is being inspected at one

time, it is recommended that the panels be assessed

individu-ally as in 6.3; but when the entire group has been rated, the

ratings should be reviewed to make sure that ratings assigned

actually reflect the relative merits of the panels This acts as a

check on individual ratings and aids in ensuring that the

inspector’s judgment or frame of reference has not changed

during the course of the inspection, owing to fatigue, change in

lighting conditions, haste to finish the job, or other causes One

method of facilitating this comparison is to remove individual

panels from their racks and place them beside other panels It

may be advisable to physically arrange all of the panels in

order to merit

7 Assignment of Appearance Rating

7.1 This recommended practice recognizes that whereas the

degree of protection afforded the substrate can be assessed

fairly objectively in accordance with Section6, the assessment

of appearance depends on many subjective factors Therefore,

the appearance rating cannot be assigned with the same degree

of precision as can the protection rating

7.1.1 There are many modes of deterioration in appearance

mentioned in 4.2 but this list is not exhaustive, and as new

plating systems are developed and introduced to industry, they

may well exhibit new types and modes of deterioration

7.1.2 Unlike the protection rating, the appearance rating is

based not only on the area of the defects but also on their

severity: the degree to which they would detract from the

commercial acceptability of an article of appearance similar to

that of the panel

7.2 The appearance rating is based, in the first instance, on

the protection rating Since corrosion of the substrate also

detracts from appearance, the appearance rating can be no

higher than the protection rating

7.2.1 If basis metal corrosion is the only defect, there being

no additional defects affecting only the coating, the appearance

rating is the same as the protection rating If there are surface

defects not accounted for in the protection rating, the

appear-ance rating will be one or more units lower than the protection

rating This lowering of the appearance rating is referred to in

what follows as the “penalty.”

7.3 The inspector must decide, on the basis of best current

practice and opinion, whether a surface coating defect is (1)

very slightly, (2) slightly (3) moderately, or (4) severely

damaging to the acceptability of the appearance Guidelines are

given below, but judgment factors inevitably enter into the

decision

7.3.1 Defects only slightly damaging may include very light

surface pitting that detracts little from the reflectivity, light

tarnish or stain easily removed by mild cleaning (such as would

be given, for instance, in normal car-washing practice), super-ficial crack patterns typical of some kinds of chromium plate, and so forth Such defects, to be categorized as “slight,” must not render the finish commercially unacceptable

7.3.1.1 A penalty of 1 or 2 points (rating numbers) is assessed for appearance defects classified as slight One point

is assessed if the defects can be classified as very slight, two if slight

N OTE 6—If fractional rating was used for the protection number, this would result in a fractional appearance rating; in that case the fractional appearance rating may be retained, or rounded off to the nearest whole number, provided, however, that the appearance rating may not be higher than the protection rating.

7.3.2 Defects moderately damaging include the same types

as in 7.3.1 but more severe, so as to render the appearance questionably acceptable from a commercial standpoint For example, surface pits that begin to detract from reflectivity; tarnish or stain that, although removable, requires more drastic treatment than routine washing

7.3.2.1 A penalty of 3 or 4 points (rating numbers) is assessed for appearance defects classified as moderate 7.3.3 Surface defects that render the panel definitely unac-ceptable in appearance are classified as severe

7.3.3.1 A penalty of 5 or more points, up to the maximum available, is assessed for severe surface defects

7.4 The procedure for checking the ratings described in

6.3.1 is of particular importance in assigning appearance ratings, and is strongly recommended

8 Low-Rated Panels

8.1 The system described in the foregoing should be satis-factory for assessing relatively good panels Difficulties may be encountered in attempting to rate severely corroded panels For example, if a panel rates as low as 4 for protection, it may be difficult to assess any additional appearance defects At the option of the inspector, this difficulty may be handled as follows:

8.1.1 A cutoff point may be chosen below which appearance ratings are deemed to be of no significance For example, it may be agreed that any panel with a protection rating of 5 is so unacceptable that an appearance rating has no meaning Such panels may arbitrarily be assigned one of two appearance

ratings: (1) if there are no obvious additional surface defects, appearance rating is set equal to protection rating; (2) if there

are any surface defects at all, no attempt is made to assess their severity and the appearance rating is 0

8.1.2 Alternatively, after setting the cutoff point as in8.1.1, the appearance rating may be disregarded and only a protection rating assigned

9 Keywords

9.1 atmospheric exposure; corrosion rating; electroplated deposits

APPENDIXES (Nonmandatory Information) X1 ABBREVIATIONS DESCRIBING DEFECTS X1.1 Types of Failure X1.1

R = corrosion (rusting) of the basis metal (Permanent or massive type of

basis metal corrosion such as that in pinholes, bare, or flaked areas,

or in craters of broken blisters.)

Rs = stain as a result of basis metal corrosion products, such as rust stain,

which can be removed readily with a damp cloth or chamois and mild

abrasive revealing a sound bright surface.

S = stains or spots other than that of obvious basis metal corrosion

products.

Sp = surface pits Corrosion pits probably not extending through to the

basis metal—that is absence of obvious basis metal corrosion

products bleeding therefrom.

F = flaking or peeling of deposit.

B = blistering.

X1.2 Degree or Extent of Pinhole Rusting, Staining,

Sur-face Pitting, Flaking, and So Forth X1.2

vs = very slight amount.

i = intermediate or moderate amount.

X1.3 Description of Blisters X1.3

s = less than about 0.5 mm in diameter.

i = about 0.5 to 2.0 mm in diameter.

x = greater than about 2.0 mm in diameter.

X1.4 Description of Location of Defects X1.4

X2 DOT CHARTS AND PHOTOGRAPHS

X2.1 The dot chart standards (Fig X2.1)4 ,5 are most

useful when assessing the degree of corrosion in industrial

locations The photographs (Fig X2.2)4 are usually more helpful when determining the extent of corrosion in marine atmospheres

5 Permission for reproduction is granted by the Chrysler Corp for use of these

charts, which are a part of the Laboratory Procedure 461-H-79.

FIG X2.1 Example of Dot Charts 4

FIG X2.1 (continued)

FIG X2.1 (continued)

FIG X2.2 Example of Corrosion Appearance

FIG X2.2 (continued)

FIG X2.2 (continued)

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